大曲率光学零件面形的空间载频外差干涉术检测

Testing large curvature surface of optical element with spatial carrier heterodyne interferometry

光学零件表面面形检测的结果直接影响光学零件的质量,介绍了一种在平面干涉仪上检测大曲率球面光学零件面形的方法,通过对干涉图进行预处理、FFT提取相位、解包裹,并采用Zernike多项式拟合,得到被检球面相对平面的面形函数,与指定的球面相减后,再一次进行Zernike多项式拟合,得到了被检面相对于指定球面的面形函数,由此计算出被检球面的面形误差PV值、RMS值,N与△N,并模拟出了用球面干涉仪检测时的干涉条纹。该方法克服了接触检测的缺点,精度高,PV值的标准差σ优于λ/100,RMS值的标准差σ优于λ/700,而且可通过软件设定检测任意大曲率光学零件,为大曲率半径光学零件的检测提供了一种适用的方法。

The quality of optical element is directly influenced by the results of its surface test. A kind of test method of optical surface with large curvature by plane interferometer was studied. The measured surface error relative to the standard plane was obtained by some pivotal techniques such as interference fringe preprocessing, FFT phase distilling, phase unwrapping and the first Zernike polynomial fitting, then it subtracted the standard sphere appointed, so the measured surface error relative to the standard sphere appointed was obtained by reusing Zernike polynomial. On the basis, PV, RMS,N, ΔN of the measured surface error were calculated, the interference fringe formed by the measured surface relative to the standard sphere was successfully simulated. The method overcame the disadvantages of contact test with high precision, the σ of PV was better than λ/100 ,the σ of RMS was better than λ/700, and it could test random large curvature through the software. It provides a suitable method to test optical surface with big curvature radius.